1. Field of the Invention
The invention relates to wet shaving implements and is directed more particularly to a wet shaving implement in which there is a plurality of blades.
2. Description of the Prior Art
It is generally known in the art to provide a housing having platform and cap portions adapted to receive a blade means therebetween. In U.S. Pat. No. 1,195,259, issued Aug. 22, 1916 to W. E. O'Reilly, there is shown a platform and cap portion formed from a single piece of metal, the cap overlying the platform.
It is also generally known to embed a blade in a plastic shaving head, the head being permanently attached to a handle, or alternatively, removable from a handle for replacement by another shaving head. U.S. Pat. No. 1,864,995, issued June 28, 1932 to T. H. Frost shows such an arrangement.
More recent examples of plastic shaving heads having blades fixed therein include U.S. Pat. No. 3,703,764, issued Nov. 28, 1972 to Roger L. Perry, U.S. Pat. No. 3,724,070 issued Apr. 3, 1973 to Francis W. Dorion, and U.S. Pat. No. 4,026,016 issued May 31, 1977 to Warren I. Nissen. While such recent examples have been eminently successful, there is, as always, a need for such products which are less expensive to manufacture and offer improved functional characteristics.
U.S. Pat. No. 3,786,563, issued Jan. 22, 1974 to Francis W. Dorion, Jr., et al, discloses geometrical relationships present in plural cutting edge systems. Among the important parameters of plural edge systems are "blade tangent angle", "exposure", and "span".
It has been discovered that a plural cutting edge shaving system in which the above geometrical relationships are maintained within critical limits provides superior shaving characteristics. Such a shaving system includes two cutting edges disposed parallel to one another and in spaced relation to provide leading and following cutting edges so that both cutting edges are successively active with respect to the hair elements being cut during a single shaving stroke. The cutting edges are supported in spaced parallel relation to one another. A guard structure is disposed in fixed relation to the cutting edges to define in part the desired geometrical relationship. Significant components of the geometrial relationship include the above referred to "blade tangent angle," "exposure," and "span."
"Blade tangent angle" is defined as the angle between the bisector of the included angle of a cutting edge and a line from the cutting edge tangent to the skin engaging surface immediately forward of that cutting edge. "Exposure" is defined as the distance from a cutting edge to a plane defined by skin engaging surfaces immediately in front of and behind the cutting edge the distance being measured perpendicularly to the reference plane, the exposure being considered positive when the cutting edge is located on the outer (skin) side of that plane and being considered negative when the cutting edge is further from the skin than that plane. "Span" is defined as the distance between the cutting edge and the skin engaging surface forward of that cutting edge.